The staining of the internal limiting membrane (ILM) is one of the important developments of surgery for such vitreo-retinal diseases as macular hole and epiretinal membranes (ERMS) (Indocyanine green-assisted peeling of the retinal internal limiting membrane. Burk S E et al. Opthalmology. 2000; 107:2010-2014). It is now widely recognized that without surgical adjuvant it is extremely difficult to remove the membranes due to the poor visibility of the ILM and ERMS. In particular, Indocyanine green (ICG) and Trypan Blue (TB) staining have greatly facilitated ILM and ERMS peeling in various vitreo-retinal diseases and as a result, this technique is now widely accepted by many surgeons However, numerous reports have recently emerged regarding retinal damage caused by intravitreal injections of ICG and TB both in experimental and clinical use. (Morphological and functional damage of the retina caused by intravitreous indocyanine green in rat eyes. Enaida H, et al. Graefes Arch Clin Exp Opthalmol. 2002; 240:209-213; Uemura A, et al. Visual field defects after uneventful vitrectomy for epiretinal membrane with indocyanine green-assisted internal limiting membrane peeling. Am J Opthalmol. 2003; 136:252-257; Veckeneer M, et al. Ocular toxicity study of trypan blue injected into the vitreous cavity of rabbit eyes. Graefes Arch Clin Exp Opthalmol. 2001; 239:698-704).
Further, creating a continuous curvilinear capsulorhexis (CCC) in eyes with a white mature cataract can be challenging as it is difficult to distinguish the anterior capsule from the underlying white cortex. Poor visualization of the capsule tends to result in an incomplete or inadequate CCC that could cause a subsequent capsular tear, vitreous loss and intraocular lens (IOL) dislocation. The intraocular administration of dyes for anterior capsule staining to perform CCC in eyes with a cataract with poor or no red reflex has become increasingly popular. Dada demonstrated that capsular staining facilitates the CCC even in immature cataracts and could be a useful adjunct for trainee surgeons. Trypan blue 0.1% and 0.06% have been introduced to capsular staining, and has been found to have no apparent toxicity in vivo. However, trypan blue has been reported to be toxic to corneal endothelium in vitro in severe conditions. Indocyanine green (ICG) is also a frequently used dye for capsular staining. McEnerney and Peyman described the use of ICG for cell counts in rabbit corneal endothelium, and suggested the dye did not damage living endothelium. However, the inventors reported the potential toxicity of ICG to retinal cells in 2002, and recently, the toxicity of ICG has been reported in retinal pigment epithelium, ganglion cells, and photoreceptors. (Indocyanine green induces apoptosis in human retinal pigment epithelial cells. Rezai K A, et al. Am J Opthalmol. 2004; 137:931-933; Trypan blue induces apoptosis in human retinal pigment epithelial cells. Rezai K A et al. Am J Opthalmol. 2004; 138:492-495).
As stated above, dyes (such as IC or TB) conventionally used for staining an ophthalmic membrane, particularly the internal limiting membrane and the anterior capsule have produced questions regarding their safety. Such doubts developed due to reports of the possibility of toxicity, teratogenicity and so on to the retinal cells. Furthermore, there were technical problems such as the inability to get a satisfactory dye at lower concentrations and complicated staining methods. Thus, such problems made ophthalmic surgery an even more difficult matter.
Accordingly, to promote the improvement of ophthalmic surgeries, the development of a dye that specifically colors an ophthalmic membrane, and has the objectives of high staining at low concentrations along with high levels of safety, has been greatly desired.